Power performance of electronic devices has received increased attention, especially as devices become smaller and portable. As great power performance increases have been made with data processing within individual device chips, communication between device chips has consumed an increased percentage of total power consumption of portable electronic devices. However, communication between device chips is necessary for the portable electronic devices to perform their intended functions, especially communication between processing resources and memory resources.
LPDDR (low power dual data rate) memory devices, and specifically LPDDR2 (low power dual data rate version 2, JESD209-2F, June 2013), LPDDR3 (LPDDR version 3, JESD209-3B, August 2013), LPDDR4 (LPDDR version 4, specification in development by JEDEC (Joint Electronic Device Engineering Council) as of the filing of this application) and future LPDDR generations, allow the use of lightly terminated or unterminated I/O (input/output) interfaces. The termination of the I/O interfaces consumes non-useful energy by converting power to heat to terminate the I/O interfaces. By allowing lighter termination or no termination on I/O interfaces, certain power savings can be achieved, albeit at the cost of reflections and/or other noise on the I/O interfaces. Reflections are echoes from previous transactions, which may travel back and forth over a signal line for some time. The size and timing of the reflections or other noise can cause the receiving device (e.g., a memory controller circuit receiving data from a memory device) to incorrectly sample the echo causing errors in the system.
Reflections are currently handled by the use of stronger termination, which suppresses static noise on the I/O interface, at the cost of wasting active power. Alternatively, access transactions can be separated in time far enough to allow the reflections to die out, which can significantly reduce memory bandwidth and performance. It will also be understood that reflections are typically not as significant in stacked (e.g., package on package (PoP)) device configurations; however, such stacked configurations only work for certain system implementations, and therefore, using stacked configurations is very limited in its ability to avoid false sampling due to noise and reflections.
Descriptions of certain details and implementations follow, including a description of the figures, which may depict some or all of the embodiments described below, as well as discussing other potential embodiments or implementations of the inventive concepts presented herein.